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Laboratory Test Directory

LAMA2 (Merosin) Gene Sequencing

Components

Name Method Department Units
LAMA2 (Merosin) Gene Sequencing Analysis of the entire coding region: Sequence analysis
Polymerase chain reaction (PCR)
Sanger sequencing
DNA extraction
Molecular Genetics

Specimen Requirements

Whole blood

Container Type Container Size Specimen Volume
Preferred

Purple tube (EDTA)

4 mL 4mL-8mL
Stability

Room temperature - 24 hour(s)
Refrigerated - 72 hour(s)

Specimen Preparation

  • Do not centrifuge
  • Do not freeze

Reasons for Rejection

  • Frozen specimen
  • Wrong collection tube
  • Clotted specimen
  • Delayed or improper handling

Comments

Please click on the Lab Form Link in the Forms Section to print and complete the Genetic Test Requisition Form. Submission of completed Genetic Test Requisition Form is required, and submission of informed consent form is recommended. If available, please also muscle biopsy results. This test is a full gene sequence analysis of the LAMA2 gene.

Presence of pathogenic variant in both alleles of the LAMA2 gene causes congenital merosin-deficient muscular dystrophy, which is inherited in autosomal recessive manner. Approximately 60-80% of patients with merosin-deficient muscular dystrophy have a pathogenic variant(s) detectable by LAMA2 full gene sequence analysis. The remainder (20%-40%) of patients have exonic deletions, which will NOT be detected by full gene sequence analysis.

The congenital muscular dystrophies (CMDs) are a genetically and clinically heterogeneous group of muscle disorders associated with hypotonia (present at birth) and delayed motor milestones followed by the development of contractures, scoliosis and muscle weakness. The inheritance of CMDs is almost always autosomal recessive and can be syndromic or non-syndromic. LAMA2-related muscular dystrophy is also known as merosin-deficient congenital muscular dystrophy type 1A (MDC1A [muscular dystrophy, congenital, type 1A]). Diagnosis of LAMA2-related muscular dystrophy is based on: clinical findings, elevated serum CK concentration, specific abnormal white matter signal on T2-weighted MRI by age one year, complete or partial laminin alpha-2 deficiency on immunohistochemical (IHC) staining of muscle and/or skin, and presence of pathogenic variant in both alleles of the LAMA2 gene. Please note, secondary deficiency of the protein laminin alpha-2 may result from another type of dystroglycanopathy. Late-onset LAMA2-related muscular dystrophy (the limb-girdle muscular dystrophy phenotype) needs to be differentiated from other forms of limb-girdle muscular dystrophy. Elbow contractures, high serum CK concentrations, and prominent spinal rigidity may lead to a phenotype overlapping with Emery-Dreifuss myopathy; however, in contrast to Emery-Dreifuss myopathy, LAMA2-related muscular dystrophy usually lacks cardiac involvement.

 

Forms

Lab Form

CPT Code

  • 81408